PROJECT SUMMARY Over the past two decades, there has been substantial growth in opioid consumption during pregnancy, diagnoses of opioid use disorder among pregnant women, and neonatal complications from in utero opioid exposure. Untreated opioid use disorder among pregnant women leads to poor outcomes for the mother and infant; however, opioid agonist treatment (OAT) for opioid use disorder is highly effective. OAT improves treatment retention, reduces relapse risk, reduces HIV-risk, reduces criminal behavior, reduces risk of overdose death, and improves birth weights. Further, ensuring access to OAT before pregnancy decreases the likelihood of illicit drug use during critical times of fetal development in the first trimester. Despite evidence that treatment is effective in mitigating adverse outcomes from opioid use disorder, evidence suggests that the vast majority of patients in need of treatment do not receive it. We will conduct a rigorous and reproducible field experiment of randomly-selected outpatient buprenorphine providers and opioid treatment programs in 10 states with a range of state policies. The study will include simulated female patients of reproductive age with randomly-selected characteristics, including pregnancy status. We aim to determine whether: 1a) pregnant women with opioid use disorder are more likely to experience difficulty accessing OAT when compared with non-pregnant women, 1b) insurance type modifies ability to access OAT, and 2) state policies promote or hinder access to treatment. The proposed study uses a rich array of methodologies and leverages an experienced research team with expertise in qualitative research, health law, addiction medicine, biostatistics, health policy, health services research, and economics. Results from this work will have immediate applicability to state policymakers tasked with using finite resources to combat the opioid epidemic and improve outcomes for this vulnerable population.